The purpose of the present proposal is the identification of the physiologic and pathophysiologic mechanisms which interact to increase or decrease the size of the cerebral ventricles. The ultimate goal of this work will be an improved understanding of the mechanisms of hydrocephalus and other disorders of cerebrospinal fluid dynamics leading to improved diagnostic and therapeutic methods. The work will be performed in three overlapping phases over three years. The first phase of the proposal consists of experiments on normal dogs to determine the effect of manipulating parameters, such as mean intracranial pressure and pulse pressure in the cerebral ventricles. These parameters can be manipulated while maintaining others constant using a pumping device designed for this purpose. The second phase involves the development and refinement of a mathematical model and associated computer simulation software incorporating the various physiologic parameters which interact to control the size of the cerebral ventricles. The final phase of the proposal will be to use the model to predict the results of various physiologic manipulations which would mirror pathologic conditions of cerebrospinal fluid dynamics. These experiments will improve understanding of the control of ventricular size and will serve to strengthen or cause to be modified the mathematical model. The project is interdisciplinary in nature combining expertise in the physiology of intracranial pressure, control systems engineering and electronic instrumentation.